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Revenue outlier capping: The cap is computed from the control arm alone · case 02

A treatment that creates more big spenders gets its gains clipped by a control-based cap.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

The cap is the nearest-rank pct-th percentile of the pooled values of both arms: sorted pooled value at 1-based rank ceil(pct/100 * N), clamped to [1, N]. Every value is capped (not dropped) at that threshold and each arm mean is taken over all its users. Empty arm -> None. Return [cap, capped control mean, capped treatment mean].

Why this case matters

Capping whales keeps revenue metrics sensitive; a per-arm cap biases the comparison itself.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
nearest rank rounds up	`[2, 1.666667, 2.0]`	`[3, 2.0, 3.0]`	Failed

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